notes 23-34 Flashcards
Aufbau Principle
as protons are added on by one to the nucleus to build up the elements, electrons are similarly added to these hydrogen-like orbitals
Hund’s Rule
the lowest energy configuration for an atom is the one having the maximum number of unpaired electrons (upe) allowed by the Pauli principle in a particular set of degenerate orbitals; generally shown as spin up
Pauli Exclusion Principle
no two electrons in an atom can have the same four numbers; electrons in the same orbital must have opposite spins
valence electrons (ve)
the electrons in the outermost principal quantum level of an atom
core electrons
inner electrons
Elements that have the same number of valence electrons…
…are in the same group which is why they have similar chemical reactivity.
Atomic Radius trend
atomic radii increases down a group and decreases across a period
Ionization Energy (IE)
the energy required to completely remove an electron from a gaseous atom or ion
Ionization Energy trend
IE decreases down a group and increases across a period (larger n → larger size → smaller IE)
Electron Affinity
the energy change associated with the addition of an electron to a gaseous atom
The greater the electron affinity…
…the greater the energy released when the electron is “captured” by the atom.
Electron Affinity trend
the electron affinity decreases (less negative) down a group and increases (more negative) across a period
Electron Affinity trend exceptions
He, Be, N, Ne, Mg, Ar
Size of Ions trend
- cations are smaller than the parent ion (removing electrons)
- anions are larger than the parent ion (adding electrons)
- ion size increases down a group
Isoelectronic Ions
ions containing the same number of electrons
Isoelectronic Ions trend
as atomic number increases the ionic radii decreases for an isoelectronic series
Paramagnetism
causes the substance to be attracted into an induced magnetic field; unpaired electrons
Diamagnetism
causes the substance to be repelled from an induced magnetic field; paired electrons
Metallic Character
metallic character increases down a group and decreases across a period
Bond Energy
the energy required to break a bond
ionic bonding
an atom loses electrons relatively easily and reacts with an atom that has a high affinity for that electron
covalent bonding
electrons are shared by two nuclei
polar covalent bonding
unequal sharing of electrons between two atoms
Electronegativity
the ability of an atom in a molecule to attract shared electrons to itself
Electronegativity trend
electronegativity decreases down a group and increases across a period; F has the highest electronegativity
dipole moment
a measure of the separation of positive and negative charge in a molecule
lattice energy
the change in energy that takes place when separated gaseous ions are packed together to form an ionic solid
single bond
a shared electron pair (sigma)
double bond
two shared electron pairs (sigma + pi)
triple bond
three shared electron pairs (sigma + 2pi)
C-C bond length
154pm
C=C bond length
134pm
C≡C bond length
120pm
enthalpy equation
ΔH = (sum of bonds broken) - (sum of bonds formed)
localized electron (LE) bonding model
a molecule is composed of atoms that are bound together by sharing pairs of electrons using the atomic orbitals of the bound atoms
lone pairs
pairs of electrons localized on an atom
bonding pairs
pairs of electrons found between atoms
Lewis structure
the arrangement of only the valence electrons in a molecule